Hi CaptainHamburguer,
The default braking in x-plane 11 is shit, try this LUA plugin. I use it with a single braking button and it works well, although you can assign left and right braking buttons if you want. The longer you hold the button the more braking force it applies. It also supports the Zibo 737 if you fly that. You can customise the braking force for each plane you have.
https://forums.x-plane.org/index.php?/files/file/37662-differential-and-progressive-brakes-for-x-plane-11/
Cheers
Mike